1. Field of the Invention
The present invention relates to a measurement instrument for information of the inside of a living body, using light.
2. Description of the Related Art
An instrument for measuring information of the inside of a living body, in a simple and convenient way without giving damage to the living body is used in a field such as clinical medical treatment or brain science or the like. Among these, in particular, a measurement method using light is a very effective tool. A first reason for that is that oxygen metabolism of the inside of a living body corresponds to a concentration of specific chromophores (such as hemoglobin, cytochrome aa3, myoglobin or the like), and the concentration of these chromophores can be determined by absorption amount of light. In addition, a second and a third reason for the optical measurement to be effective include the facts that light is simply and conveniently handled by an optical fiber, and furthermore, use thereof within a range of a safety standard does not give damage to the living body.
An optical measurement instrument for the living body for measuring the inside of a living body, by using light with a wavelength region from visible rays to infrared rays, by utilization of such advantages of the optical measurement, is described, for example, in Patent Document 1 or Patent Document 2. The optical measurement instruments for the living body described in these documents acquire the living body information such as blood circulation, hemodynamics, hemoglobin change or the like, from the detected light power, by emission of light by a semiconductor laser, introducing thus emitted light by an optical fiber to irradiate onto the subject, detecting light transmitting through or reflecting from the inside of the living body, and introducing the detected light by the optical fiber to a photodiode.
In addition, to realize such optical measurement for the living body, an optical measurement probe for the living body, where the optical fiber is contacted with the subject, is used: it is composed of the irradiation part for irradiating light, the light detection part for detecting light transmitting through or reflecting from the inside of the subject, and an immobilization member for immobilizing the irradiation part and the light detection part, by arranging them in a lattice way or a network way. In addition, this immobilization member has a shape so that the irradiation part and the light detection part are contacted with the subject, by using a band or a rubber string or a hair band or the like. As an example of this optical measurement probe for the living body, Patent Document 3 or the like is included. In addition, the optical fiber is usually present in plural, and the optical measurement probe for the living body, having a structure for bundling this plurality of optical fibers, is described in Patent Document 4, Patent Document 5, Patent Document 6, Patent Document 7, Patent Document 8, Patent Document 9 or the like.
In the above Patent Documents, the optical measurement is realized by introducing light emitted at the main body of the instrument to the living body via the optical fiber, however, it is desirable that the optical fiber is not used to realize more simple and convenient measurement and to reduce load to the subject. Conventional technologies realizing simple and convenient measurement by removing the optical fiber are described in Patent Document 10, Patent Document 11 or the like. They are technologies for acquiring living body information by wireless control, which are provided with a light source and a light receiver to the optical measurement probe for the living body.    Patent Document 1: JP-A-9-98972    Patent Document 2: JP-A-9-149903 (corresponding to US2001/0018554)    Patent Document 3: JP-A-8-117209    Patent Document 4: JP-A-2001-286449    Patent Document 5: JP-A-2002-11012    Patent Document 6: JP-A-2003-322612    Patent Document 7: JP-A-2004-205493 (corresponding to US2006/0058594)    Patent Document 8: JP-A-2004-248961    Patent Document 9: JP-A-5-93403    Patent Document 10: JP-A-9-140715    Patent Document 11: JP-A-2002-150123 (corresponding to US2003/0093361)
In the optical measurement for the living body, it is one of the most important problems to reduce load given to the living body to as low as possible. Contacting of the optical measurement probe for the living body which is composed of the optical fibers (hereafter referred to as a probe), with the living body as the subject, to realize the optical measurement for the living body, is considered to limit a movable range of the living body, depending on the length of the optical fiber, or to give load to the living body due to weight of the optical fiber. From such viewpoints, a compact and lightweight optical measurement instrument for the living body, without using the optical fiber has been required, to realize the optical measurement for the living body in a more natural state. Therefore, in the conventional technologies, the optical fiber is removed by arranging the light source and a detector on the inside of a probe, however, it requires installing of the driving device for the light source at a place connectable with the light source by an analog electric signal, which requires arrangement of the driving device for the light source on the inside of a probe, to suppress all electric or supposed noises to as low as possible. In addition, arrangement of a plurality of the light sources on the inside of a probe, to acquire multiple pieces of living body information, requires a plurality of driving devices for the light sources, resulting in increase in weight and volume thereof, and increase in load given to the subject. Accordingly, such a compact sized and lightweight optical measurement instrument for the living body has not been realized until now, that does not use the optical fiber and is capable of acquiring many pieces of living body information.